1. Field of the Invention
This invention relates to devices and methods for making fixed dental bridges. More specifically, this invention relates to methods and devices for making fixed bridges which involve the use of lost wax techniques.
2. Background of the Prior Art
Tooth loss due to decay, injury or the like can necessitate the need for replacement using fixed bridges. A fixed bridge is a tooth or series of teeth anchored to existing healthy teeth to replace and fill gaps or omissions in the patient's mouth. The replacement teeth can be constructed of porcelain, inert metals, or mixtures of the two.
The preferred method of producing a fixed bridge involves the use of a "lost wax" technique. The lost wax technique is well known in the art. In a lost wax casting, a wax form resembling the tooth or teeth to be cast in prepared and positioned. A mold is formed around the wax. A molten material such as an inert metal is poured into the mold, melting the wax as it enters. The molten material is permitted to solidify after which the mold is opened leaving a casting of the appropriate tooth shapes. Procelain or other aesthetic material can, then, be applied to the outer suface of the metal casting to provide an aesthetically pleasing surface which resembles natural teeth. Various methods have been proposed for the manufacture and installation of the wax bridge or pre-mold. Most of these methods involve taking an impression of the patient's mouth, and preparing a cast model from the impression. The gaps caused by missing teeth can, then, be filled with appropriate wax sculpted members. These members can, then, be used to form a mold to cast the fixed bridge.
To date, there are two methods of constructing the wax pre-molds. The older method involves individual sculpting of a wax plug into the appropriate tooth shapes. This method requires a great deal of artistry and talent to ensure that the tooth shapes prepared will be properly oriented and will yield suitable cast members. The second method involves the use of individual wax tooth shapes or pontics. The individual pontics must be placed in position in the appropriate gap and held while they are molded together. This method is incredibly tedious and prone to error as each pontic must be individually positioned with respect to tooth height, tooth spacing and orientation in opposition to the opposed jaw member.
It is to be understood that the pontics must be specifically oriented to ensure an appropriate bite. This means that the pontic must be positioned precisely in relation to the existing teeth on either side of it and must also have correct cusp to fossa relationship. Any variance will cause an incorrect bite and can, potentially, damage the surrounding or opposing teeth. Because of the precise positional requirements, the individuals preparing the wax casting for the fixed bridge must be highly skilled. Even so, the opportunity for error and mistake is great.
Thus, it would be desirable to provide a device and method for preparing the wax pre-casting in which the individual pontics could be readily adjusted for gap, orientation and the like. It is also desirable that a method and device be provided which will permit accurate orientation of the individual pontics with no undue experimentation or manipulation.